Document NKr2J75bO89ene494vJoKG3D

1060 Proceedings of the 49th ASMS Conference on Mass Spectrometry and Allied Topics, Chicago, Illinois, May 27-31, 2001 Determination of Anionic Perfluorinated Surfactants by LC ESI MS Melissa M. Schultz1; Donald A. Griffin1; Cheryl A. Moody3; Scott A. Mabury3; Douglas F. Barofsky1; Jennifer A. Field2 Department o f Chemistry1 and Department o f Environmental & Molecular Toxicology2, Oregon State University, Corvallis, OR 97331 Department o f Chemistry3, University o f Toronto, Toronto, Ontario, Canada, M5S 3H6 Introduction Concern over the environmental impact of perfluorinated carboxylates and sulfonates has been increasing since they were discovered recently in samples of human and marine blood plasma. They are globally distributed, including in polar regions (urban _ 1 ppm, remote _ 0.1 ppm).' Perfluorinated surfactants have many applications in industrial processes and in commercial products. Some of these uses include: fire-fighting foams, protection and repellant products, cosmetics, herbicide and insecticide formulations, wide range of cleaners (carpet, windows, cars, floors), and coatings on paper products.2 Given the high energy of the carbon-fluorine bond, the perfluorinated sulfonates and carboxylates have not been found to biodegrade under aerobic or anaerobic conditions.3 Thus, these compounds are very persistent in the environment, leading the 3M Company (St. Paul, MN) to discontinue their production by 2002. Methods and Instrumentation A quantitative method was developed in this laboratory for the analysis of perfluorinated carboxylates and sulfonates in groundwater using reverse-phase HPLC coupled with ESI MS. The 10 cm x 0.32 mm reverse phase column packed with 5 m Ultracarb 30 ODS (Phenomenex, Torrance, CA). The columns are made in house using a balanced density packing method. The solvents are water and methanol, each 5 mM NH4F. The solvent gradient is 40-100% methanol over 10 minutes and with a 10 minute hold at 100%. The LC is directly interfaced to the electrospray ionization source of a Finnigan LC-Q ion trap mass spectrometer (Finnigan, San Jose, CA). The ion trap is operated in full scan (200-600 u) mode for quantitation. A solid phase extraction step was incorporated to improve reproducibility. A 0.5 gram styrene-divinyl benzene sorbent phase (Supelco) is used. The sorbent phase is conditioned with 5 mL of acetonitrile, 5 mL of methanol, and 5 mL of water. The groundwater sample is spiked with a surrogate (perfluorodecanoate) and passed through the sorbent. The analytes of interest are eluted off with two 3 mL aliquots of methanol. The elution is spiked again with an internal standard (perfluoroundecanoate). The elution containing the analytes o f interest is then diluted with millipore water so that it will fall into the LC-Q's linear range. Results and Discussion Separation of the various carbon-chained perfluorinated carboxylates and sulfonates was achieved and their molecular ions were observed and employed for quantitation. The combined use of 5 mM ammonium fluoride buffer and a column heated to 35 C was found to drastically reduce chromatographic carryover. A rarely observed m/z 499 interference was observed in some animal tissues.1 Although this interference was unlikely in groundwater, a standard, a contaminated groundwater sample, and a spiked contaminated groundwater sample were analyzed with tandem mass spectrometry. The 499 > 80 and 499 > 99 transitions were monitored and differed by 30% which indicates that no m/z 499 interference was present. Calibration curves for quantitating the various carbon-chained perfluorinated surfactants were generated from aqueous solutions of the standards spiked with an internal standard. All calibration curves were linear (r2 .99). Detection limits ranged from 10 pg. to 25 pg. for the various carbon chained perfluorinated surfactants. rr-.o ~n C"J r-o ro po ro CONTAIN! NO OR' I Proceedings of the 49th ASMS Conference on Mass Spectrometry and Allied Topics, Chicago, Illinois, May 27-31, 2001 F ig ur e 1: Periluorosulfonales and carboxylates in groundwater samples from W AFB The procedure was applied to contaminated groundwater samples from Wurtsmith Air Force Base, Ml. Figure 1. shows the selected ion chromatogram for perfluorosulfonates and carboxylates in groundwater taken from one of the contaminated wells. To improve reproducibility, a solid phase extraction sample preparation step was employed to eliminate inorganic ions that are present in many groundwater matrices that can interfere or suppress electrospray ionization. As a result, the peak resolution improved and the detection limits decreased. The reproducibility also improved, in some cases by a factor of 8. The methodology is adaptable to the analysis of wastewater from a municipal wastewater treatment plant. Figures 2 and 3 show an analysis of perfluorosulfonate in the primary sewage effluent and secondary effluent from a municipal wastewater treatment plant. Conclusions Qualitative and quantitative determinations of perfluorinated carboxylates and sulfonates are possible with LC ESI MS. Solid phase extraction aides in reproducibility, improvement in peak shape, and in lowering the detection limits. This methodology can be adapted to a municipal wastewater treatment plant. References 1. Kannan, K. et al. Environ. Sci. Technol. 2001, 33, 1593-1598. 2. Key, B.D. et a l Environ. Sci. Technol., 1997, 31, 2445-2454. 3. Remde, A: Debus, R. Chemosphere, 1996, 52, 1563. Acknowledgments This work was supported by grants from the National Institute of Environmental Health Sciences (ES 00040).